Saturday, July 30, 2011

The Phoenix Project - Torturous Rack Question

My Nitto M12 rack and cantilever mount bolts arrived a day or so ago and I got to tinkering around with them today.

Like all things Nitto, the M12 rack is a splendid wonder. Beyond the obvious use as a support for a handlebar bag and light, I really appreciate the threaded hole on the underside of the crossbar as a third fender mounting point. On rough, gravelly roads, an unsupported forward extension of long front fenders shakes around a bit much for my tastes.

The cantilever brake mounting points also make this a real clean installation. I had a similar Nitto on my previous Trek 620, but back in those dark days, the only option available was p-clamps on the forks. This worked fine, but was a little ugly:

So quivering with anticipation at this new super sanitary configuration, I try to slip this onto the fork just to see how this is going to look and....

The rack's fork crown strut won't go through the hole in the fork crown. Some investigation reveals that the fork crown hole is threaded:

Ditto for the hole on the back of the fork crown:

I don't have my old Trek 620 around, but I'm pretty sure that the fork crown holes on it were unthreaded. I'm positive my wife's 720 is unthreaded. It is a different fork crown to be sure, but why would a Trek 620 and Trek 720 from the same years differ in fork crown hole threading or not-threading? One of those old bike mysteries, sort of like the Sphinx, we'll just never know....

Fortune smiles upon us though, as this is the same thread size as on the rack strut:

So I think, great, I'll just screw it on, there is a certain elegance to this, I'd put a rubber washer on the strut to take up whatever small gap would result when in final position.

Unfortunately, the threads on the rear hole are not coordinated with the front, so it can't screw all the way through:

So maybe I could cut the strut? Seems simple, although I hate to defile this lovely Nitto item. Furthermore, another consideration in this is that the rack's fork crown strut is intended to be used with the fork crown daruma for the really zowie fenders that are going to knock everyone out when I unveil them. Although it would probably be ok, I'm not crazy about hanging the fork crown daruma off a bolt that is not supported at both ends.

And even if it did screw all the way through, it is very unclear that the rack's cantilever struts could fit over the neato cantilever mount posts without severe bending of the rack.

The rack is steel, so it may be ok bending it. But if it is not, I could, after screwing the rack into the fork crown, thread a stud through the rack cantilever strut, then through a nut and finally into the cantilever frame post. Tighten the nut to secure the brake arm, then put a cap nut on the stud to secure the rack.

Seems like it would work, huh?

Well, well, this is one of those shop moments where we are either at the beginning of either a really elegant solution or the first steps on a "To Build A Fire" experience.

Right now, I'm mulling over my options, here are the choices as I see them:

1) Return the rack and figure something else out. I still am going to have to figure out the fork crown daruma issue, though.

2) Drill, baby, drill both holes. That makes everything else easy - no daruma worries, use the neato cantilever bolts. But I sure hate to drill an old frame...

3) Drill either the front or rear hole, that way the thread coordination issue disappears. This fully supports the daruma, but potentially requires homebrew canti mounts.

4) File off the threads on a portion of the rack strut. That way, I could screw the leading threads through the front hole, then when those threads encounter the rear hole, the portion of the stud in the front hole would have no threads and just pull through. This also potentially requires homebrew canti mounts.

5) Cut the rack strut so that it is too short to reach the rear hole. This mean that the fender daruma is on a bolt supported at only one end. This also potentially requires the custom canti mounts.